Allow HTTP partial response (2600hz#3967)

* Allow HTTP partial response * Added documentation for range request
Veilen · Jul 20, 2017 · 785b9af · 785b9af
1 parent 531cacd
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diff --git a/applications/crossbar/doc/basics.md b/applications/crossbar/doc/basics.md
@@ -234,3 +234,17 @@ curl -v \
     -H "Content-Type: application/json" \
     http://{SERVER_URL}:8000/v2/accounts/{ACCOUNT_ID}?pretty_print=true
 ```
+
+#### Requesting a range of binary data
+
+It is useful to be able to get just a section of a file when streaming or
+resuming a download. This can be accomplished with the range header, eg:
+
+```shell
+curl -v \
+    -H "X-Auth-Token: {AUTH_TOKEN}" \
+    -H "Content-Type: application/json" \
+    -H "Accept: audio/mpeg" \
+    -H "Range: bytes={START_BYTE}-{END_BYTE}" \
+    http://{SERVER_URL}:8000/v2/accounts/{ACCOUNT_ID}/vmboxes/{VMBOX_ID}/messages/{MESSAGE_ID}/raw
+```
diff --git a/applications/crossbar/src/api_resource.erl b/applications/crossbar/src/api_resource.erl
@@ -38,6 +38,7 @@
         ,multiple_choices/2
         ,generate_etag/2
         ,expires/2
+        ,get_range/2
         ]).
 
 -include("crossbar.hrl").
@@ -779,7 +780,28 @@ to_binary(Req, Context, 'undefined') ->
     RespData = cb_context:resp_data(Context),
     Event = api_util:create_event_name(Context, <<"to_binary">>),
     _ = crossbar_bindings:map(Event, {Req, Context}),
-    {RespData, api_util:set_resp_headers(Req, Context), Context};
+    %% Handle HTTP range header
+    case cb_context:req_header(Context, <<"range">>) of
+        'undefined' ->
+            {RespData, api_util:set_resp_headers(Req, Context), Context};
+        RangeHeader ->
+            RangeData={Content, Start, End, Length, FileLength} = get_range(RespData, RangeHeader),
+            ErrorCode = resp_error_code_for_range(RangeData),
+            Setters = [{fun cb_context:set_resp_data/2, Content}
+                      ,{fun cb_context:set_resp_error_code/2, ErrorCode}
+                      ,{fun cb_context:add_resp_headers/2
+                       ,[{<<"Content-Length">>, kz_term:to_binary(Length)}
+                        ,{<<"Content-Range">>, kz_term:to_binary(io_lib:fwrite("bytes ~B-~B/~B", [Start, End, FileLength]))}
+                        ,{<<"Accept-Ranges">>, <<"bytes">>}
+                        ]
+                       }
+                      ],
+            NewContext = cb_context:setters(Context, Setters),
+            %% Respond, possibly with 206
+            {'ok', Req1} = cowboy_req:reply(kz_term:to_binary(ErrorCode), cb_context:resp_headers(NewContext), Content, Req),
+            {'halt', Req1, NewContext}
+    end;
+
 to_binary(Req, Context, Accept) ->
     lager:debug("request has overridden accept header: ~s", [Accept]),
     case to_fun(Context, Accept, 'to_binary') of
@@ -789,6 +811,27 @@ to_binary(Req, Context, Accept) ->
             (?MODULE):Fun(Req, Context)
     end.
 
+-type range_response() :: {ne_binary(), pos_integer(), pos_integer(), pos_integer(), pos_integer()}.
+
+-spec get_range(ne_binary(), ne_binary()) -> range_response().
+get_range(Data, RangeHeader) ->
+    FileLength = size(Data),
+    lager:debug("recieved range header ~p for file size ~p", [RangeHeader, FileLength]),
+    {Start, End} = case cowboy_http:range(RangeHeader) of
+                       {<<"bytes">>, [{S, 'infinity'}]} -> {S, FileLength};
+                       {<<"bytes">>, [{S, E}]} when E < FileLength -> {S, E + 1};
+                       _Thing ->
+                           lager:info("invalid range specification ~p", [RangeHeader]),
+                           {0, FileLength}
+                   end,
+    ContentLength = End - Start,
+    <<_:Start/binary, Content:ContentLength/binary, _/binary>> = Data,
+    {Content, Start, End - 1, ContentLength, FileLength}.
+
+-spec resp_error_code_for_range(range_response()) -> 200 | 206.
+resp_error_code_for_range({_Content, _Start, _End, FileLength, FileLength}) -> 200;
+resp_error_code_for_range({_Content, _Start, _End, _Length, _FileLength}) -> 206.
+
 -spec send_file(cowboy_req:req(), cb_context:context()) -> api_util:pull_file_response_return().
 send_file(Req, Context) ->
     lager:debug("run: send_file"),

diff --git a/applications/crossbar/test/api_resource_test.erl b/applications/crossbar/test/api_resource_test.erl
@@ -0,0 +1,14 @@
+-module(api_resource_test).
+
+-include_lib("eunit/include/eunit.hrl").
+
+get_range_test_() ->
+    FullBinary = <<"abcdefg">>,
+    [?_assertEqual({<<"a">>, 0, 0, 1, 7}, api_resource:get_range(FullBinary, <<"bytes=0-0">>))
+    ,?_assertEqual({<<"bcd">>, 1, 3, 3, 7}, api_resource:get_range(FullBinary, <<"bytes=1-3">>))
+    ,?_assertEqual({<<"g">>, 6, 6, 1, 7}, api_resource:get_range(FullBinary, <<"bytes=6-6">>))
+    ,?_assertEqual({FullBinary, 0, 6, 7, 7}, api_resource:get_range(FullBinary, <<"bytes=0-6">>))
+     %% Invalid should give full size
+    ,?_assertEqual({FullBinary, 0, 6, 7, 7}, api_resource:get_range(FullBinary, <<"bytes=0-9">>))
+    ,?_assertEqual({FullBinary, 0, 6, 7, 7}, api_resource:get_range(FullBinary, <<"">>))
+    ].